The invention relates to a flow sensor element having film resistors, in particular having a temperature sensor based on a platinum thin-film resistor and a heat output sensor based on a platinum thin-film resistor. Advantageously, the temperature sensor and the heat output sensor are arranged on a carrier element. Electrically conductive tracks and connection surfaces for the electrical contacting of temperature sensors and heat output sensors arranged on a ceramic substrate have proven effective. In addition, the invention relates to the production and application of such a flow sensor element.
Such flow sensor elements are known from European patent application publication EP 1 065 476 A1. There, a thermal air flow sensor is disclosed, in which a sensor element having a heating resistor and a resistive temperature-measuring element is arranged countersunk in a recess of a ceramic laminate body and fixed with ceramic cement. Due to the adhesive bond and the countersunk arrangement of the sensor element with or in the ceramic laminate, the sensor element exhibits marked reactive inertness for changes in temperature of the measurement medium. The electrical contacts are covered in the flow region with an epoxy resin, so that the device cannot be used at temperatures above 300° C. In addition, the arrangement is complicated and therefore cost-intensive.
German published patent application DE 102 25 602.0 discloses a temperature sensor having a total thickness of 10 to 100 μm, which has a metallic film substrate with an electrically insulating coating, on which a platinum thin-film resistor is arranged as a temperature-sensitive element. The temperature sensor is used in the region of a cooling body for a semiconductor component.
German published patent application DE 195 06 231 A1 discloses a hot-film anemometer having a temperature sensor and a heat output sensor. The heat output sensor is arranged like a bridge in a recess of a plastic carrier plate. The platinum temperature thin-film elements for the temperature sensor and for the heat output sensor are arranged on a ceramic substrate, which is advantageously formed from aluminum oxide.
German published patent application DE 199 41 420 A1 discloses a sensor element for temperature measurement on a metallic substrate, which has an insulation layer as a membrane. Here, the membrane spans a recess in the metallic substrate. The platinum thin film is here arranged on the membrane in the region of the recess.
German published patent application DE 101 24 964 A1 discloses a sensor for measuring flow rates of gases or liquids, the sensor having a carrier membrane constructed in the form of a flag. The carrier membrane is advantageously formed of a plastic and features an electrically conductive track made of platinum and electrical feed lines. The use of such a sensor having a carrier membrane made of plastic is not possible above 300° C.
European patent application publication EP 1 431 718 discloses a quick-response flow sensor element for measuring mass flow rates of hot gaseous or fluid media. For this purpose, a temperature-measuring element and a heating element each have a metallic carrier film with an electrically insulating coating, on which the platinum thin-film resistors are arranged. Contamination causes the measured value to drift.